The present invention relates to a stereo image measuring apparatus for displaying stereo images and effecting three-dimensional measurement and a correlation process on a screen for displaying the stereo images, and particularly to a stereo image measuring apparatus capable of displaying a part of images at a large enlargement ratio, easily taking hold of measuring points and effecting a correlation process after feature points have been extracted in the vicinity of the position where each cursor exists.
A technique for analyzing stereo images has heretofore been used, for example, in a photogrammetry field, particularly for the creation of a topographical map.
When it is desired to analyze the stereo images, it is necessary to retrieve either one of left and right positions and the other corresponding points corresponding to the one position. As a method of retrieving the corresponding points, there were used those such as a visual observing method and a method using a correlation process, etc. Any of these retrieval methods was effected so as to three-dimensionally display only a portion of the stereo images.
However, the conventional method of locally displaying only the portion of the stereo images develops a problem from the standpoint of the efficiency of measuring work in that it is difficult to measure the displayed local image while deciding to which position the local image corresponds over the entire image because the stereo images displayed on a monitor are represented at a relatively high magnification.
In recent years, a process for three-dimensionally analyzing digital images obtained from a CCD camera or the like has been actively effected. There has been a strong demand for the appearance of a stereo image displaying apparatus which enables one to freely varying the magnification of each image regardless of a photographing distance of the camera and measuring the image with high accuracy.
There is a situation in which when each position is measured to draw a border or contour line or the like corresponding to an object to be measured, points for the next border line are not displayed on a display screen. It is therefore necessary to simultaneously scroll stereo images and line drawings. However, the scrolling work has a problem in that the transfer of image data and the drawing of line drawings wastes time and does not lend itself to efficient image measurement.
Further, the conventional method of locally displaying the portion of the stereo images was often effected with due regard to feature points suitable for correlation because the designation of measuring points was manually effected by a measurer.
Therefore, even if a correlation process for determining corresponding points is effected, there is a case in which the corresponding points cannot be reliably obtained. Therefore, there has been a strong demand for the appearance of a stereo image measuring apparatus capable of reliably retrieving the corresponding points.